The present invention relates to a refrigerant cycle system and its condenser, both of which are suitable for air conditioning of a vehicle and the like. In particular, they are capable of properly controlling a circulating refrigerant by varying an amount of a liquid refrigerant accumulated in a gas-liquid separator even when a flow amount of the circulating refrigerant decreases.
Inventors of the present invention proposed a refrigerant cycle system to control a super-heating degree of a refrigerant at an outlet of an evaporator in U.S. Pat. No. 6,427,480. The system in a related art in the above patent is different from a conventional receiver refrigerant cycle system and a conventional accumulator refrigerant cycle system.
In detail, basic structure of the refrigerant cycle system in the related art is shown in FIG. 6. Structure of a condenser 2 in the refrigerant cycle system is shown in FIG. 7. The condenser 2 includes a first heat exchange unit 5 and a second heat exchange unit 6. Both ends of tubes 15 included in the two heat exchange units 5, 6 communicate with a first and a second header tanks 17, 18, which are separately disposed in right and left sides of the two heat exchange units 5, 6. The first header tank 17 includes an inlet joint 24 into which a refrigerant discharged from a compressor 1. The first header tank 17 is furthermore integrated with a gas-liquid separator 7. A gas refrigerant bypass path 33 is provided to fluidly intermediate between an upper space 17a of the first header tank 17 and a mixing chamber 31 within the gas-liquid separator 7. The gas refrigerant bypass path 33 enables a separated part of the refrigerant discharged through the inlet joint 24 to directly flow into the mixing chamber 31.
A refrigerant inlet path 34 is provided for a separated part of a liquid refrigerant condensed in the first heat exchange unit 5 to flow into the mixing chamber 31 from an intermediate space 17bxe2x80x2 of the first header tank 17.
A gas return communication path 40 and a liquid return communication path 39 are provided for a gas refrigerant and a liquid refrigerant in the gas-liquid separator 7 to return to a lower space 17c of the first header tank 17. A restrictor 80 is provided between the intermediate space 17bxe2x80x2 and the lower space 17c. Here, the intermediate space 17bxe2x80x2 is a branching point to the refrigerant inlet path 34, and the lower space 17c is a converging point of the gas return communication path 40 and the liquid return communication path 39. The restrictor 80 is formed in a lower partition plate 19bxe2x80x2 disposed within the first header tank 17.
Pressure difference is generated between both the sides of the restrictor 80. This causes a part of a liquid refrigerant that is in middle of a condenser refrigerant flow path (in the intermediate space 17bxe2x80x2) to move to the gas-liquid separator 7 through the refrigerant inlet path 34. It also leads the gas refrigerant and liquid refrigerant in the gas-liquid separator 7 to the lower space 17c. 
In the related art, a part of the refrigerant discharged from the compressor 1 is directly introduced to the gas-liquid separator 7 and mixed with the liquid refrigerant from the refrigerant inlet path 34. The liquid refrigerant is then separated from the gas refrigerant so as to be accumulated in the bottom of the gas-liquid separator 7. This structure varies dryness degree of a refrigerant flowing into the gas-liquid separator 7 according to super-heating degree of the refrigerant discharged from the compressor 1. A accumulated amount of the liquid refrigerant accumulated in the gas-liquid separator 7 is thereby controlled based on the super-heating degree of the refrigerant discharged from the compressor 1. The control of the accumulated amount of the liquid refrigerant leads to control of a flow amount of a circulating refrigerant within the cycle. This results in controlling the super-heating degree of the refrigerant discharged from the compressor 1, and furthermore super-heating degree of a refrigerant at an outlet of an evaporator 4.
As explained above, in the refrigerant cycle of the related art, the control of the accumulated amount of the liquid refrigerant leads to the control of the super-heating degree of the refrigerant at the outlet of the evaporator 4. A fixed restrictor or a variable restrictor that responds to state of a high-pressure refrigerant can be therefore adopted as a decompression device 3. In comparison with the known receiver cycle, there is an advantage in eliminating an expensive and complicatedly-structured thermal expansion valve that is necessary as the decompression device in the receiver cycle.
The known accumulator cycle is equipped with an accumulator in an outlet of an evaporator (at a lower pressure side of the cycle). In comparison with the accumulator cycle, installing of the gas-liquid separator 7 at a higher pressure side of the cycle enables the gas-liquid separator 7 to be downsized due to a small specific volume of the refrigerant at the higher pressure. Furthermore, the circulating flow amount of the refrigerant within the cycle can be controlled in direct response to the super-heating of the refrigerant discharged from the compressor 1. Thereby the circulating flow amount is properly controlled, and cycle efficiency is enhanced in comparison with the accumulator cycle.
In the refrigerant cycle of the above related art, as an experimental result, it is observed that a control characteristic of the flow amount of the refrigerant worsens when the circulating flow amount of the refrigerant within the cycle is small. Here, being small of the circulating flow amount of the refrigerant is comparable to being low of a revolution speed of the compressor 1 or being low of a heat load of cooling of the evaporator 4.
In detail, when the circulating flow amount of the refrigerant is large, as shown in FIG. 3C, a liquid refrigerant (shaded part) condensed in a lower path (in a refrigerant flow of arrow b) of the first heat exchange unit 5 is increased. Liquid refrigerant ratio in the intermediate space 17bxe2x80x2 is thereby increased. The pressure difference generated between both sides of the restrictor 80 hence leads the liquid refrigerant in the intermediate space 17bxe2x80x2 to the gas-liquid separator 7 through the refrigerant inlet path 34. Here, being large of the circulating flow amount of the refrigerant is comparable to being high of the revolution speed of the compressor 1 or being high of the heat load of the cooling of the evaporator 4.
By contrast, when the circulating flow amount of the refrigerant is small, as shown in FIG. 3D, a liquid refrigerant (shaded part) condensed in the lower path (in the refrigerant flow of arrow b) of the first heat exchange unit 5 is decreased. The liquid refrigerant ratio in the intermediate space 17bxe2x80x2 is thereby decreased. The liquid refrigerant in the intermediate space 17bxe2x80x2 is thereby less likely lead to the gas-liquid separator 7 through the refrigerant inlet path 34.
As a result, when the circulating flow amount of the circulating refrigerant is small, the accumulated amount of the liquid refrigerant in the gas-liquid separator 7 is excessively decreased in relation to the super-heating degree of the refrigerant discharged from the compressor 1. Thereby the refrigerant circulating within the cycle is balanced in an excessively large amount in relation to the heat load of the cooling. The excessive large amount of the circulating refrigerant leads to decrease of the super-heating of the refrigerant at the outlet of the evaporator 4, which results in compressing the liquid refrigerant in the compressor 1.
An object of the present invention is to provide a refrigerant cycle system capable of properly controlling a circulating refrigerant even when a flow amount of the circulating refrigerant decreases.
To achieve the above object, a refrigerant cycle system is provided with the following. A first and second heat exchange units are serially disposed. A gas-liquid separator is disposed for accepting a part of a refrigerant discharged from a compressor and a part of a refrigerant from the first exchange unit to separate the flowing refrigerants into a gas and liquid refrigerants. A primary refrigerant flow path is included in the first heat exchange unit for leading a refrigerant to the second heat exchange unit, while a branch refrigerant flow path is included in the first heat exchange unit and independently separated from the primary refrigerant flow path for leading a refrigerant to the gas-liquid separator.
This structure enables the refrigerant that passes through the branch refrigerant flow path to directly flow into the gas-liquid separator. Thereby, even in operation condition where a flow amount of a circulating refrigerant decreases, the liquid refrigerant condensed in the branch refrigerant flow path is securely lead to the gas-liquid separator. Consequently, an amount of the liquid refrigerant is properly accumulated in the gas-liquid separator in correspondence with super-heating degree of the refrigerant discharged from the compressor. Thereby the flow amount of the refrigerant circulating within the cycle is properly controlled according to heat load of cooling. Furthermore, a restrictor in a related art becomes dispensable, which causes pressure loss in the restrictor to be decreased at a high flow amount. The circulating flow amount thereby increases to enhance cooling capability of the refrigerant system.
In one embodiment of the invention, tubes are disposed in parallel with each other inside the heat exchange units while fluidly intermediating between the respective header tanks. Here, the branch refrigerant flow path is separated from the primary refrigerant flow path due to a partition plate disposed inside one of the header tanks. This enables the branch refrigerant flow path to be easily formed with the partition plate inside the header tank.